In recent years, in view of energy saving and environmental conservation, illumination apparatuses using light-emitting diodes (hereinafter also referred to as “LED”) as light sources, (such as LED bulbs), have been used in place of incandescent lamps. However, the conventional illumination apparatuses using LED as a light source emit light only forward, and cannot emit light in a wide range direction unlike incandescent lamps. Therefore, the conventional illumination apparatuses cannot extensively illuminate a room by using reflected light from the ceiling or the walls unlike incandescent lamps.
To bring the light distribution characteristics of the illumination apparatus using LED as a light source close to those of the incandescent lamps, it is suggested to distribute light emitted from the LED behind the LED with the shape of a cover shading the LED (see, e.g., PTLS 1 and 2).
FIG. 1 is a schematic diagram illustrating the configuration of an illumination apparatus set forth in PTL 1. As illustrated in FIG. 1, LED bulb 101 has LED module 102, base body part 103 on which LED module 102 is mounted, and globe 104 attached to base body part 103. The sectional shape of globe 104 is a domed shape, and the outer diameter D1 of an attachment part to base body part 103 is smaller than the outer diameter D2 of the part having the maximum diameter. Thus, PTL 1 sets forth an example in which backward light distribution is increased by forming globe 104 such that the outer diameter D1 of the attachment part is smaller than the maximum outer diameter D2.
FIG. 2 is a schematic diagram illustrating the configuration of an illumination apparatus set forth in PTL 2. As illustrated in FIG. 2, the illumination apparatus includes at least one light source 105, light source substrate 106 on which light source 105 is mounted, and a cover member 107 shading the periphery of a light emission part of light source 105 and having transparency and light diffusion characteristics. Maximum outer diameter W portion in the direction orthogonal to central axis A of cover member 107 is positioned closer to light source 105 than is center C of cover member 107 in the direction of central axis A. Thus, PTL 2 sets forth an example in which backward light distribution is increased by forming cover member 107 such that maximum outer diameter W portion of cover member 107 is positioned closer to light source 105 than is center C having the dimension of cover member 107 in the direction of central axis A.